Knockdown of Arginase I Restores NO Signaling in the Vasculature of Old Rats

• Published in: Hypertension (Dallas, Tex. 1979) Vol. 47; no. 2; pp. 245 - 251
• Main Authors: White, Anthony R, Ryoo, Sungwoo, Li, Dechun, Champion, Hunter C, Steppan, Jochen, Wang, Danming, Nyhan, Daniel, Shoukas, Artin A, Hare, Joshua M, Berkowitz, Dan E
• Format: Journal Article
• Language: English
• Published: Philadelphia, PA American Heart Association, Inc 01.02.2006; Hagerstown, MD Lippincott
• Subjects: Acetylcholine - pharmacology; Aging - metabolism; Animals; Aorta - drug effects; Aorta - metabolism; Arginase - genetics; Arginine - pharmacology; Arterial hypertension. Arterial hypotension; Biological and medical sciences; Blood and lymphatic vessels; Calcium - metabolism; Cardiology. Vascular system; Clinical manifestations. Epidemiology. Investigative techniques. Etiology; Drug Synergism; Enzyme Inhibitors - pharmacology; Experimental diseases; In Vitro Techniques; Male; Medical sciences; Nitric Oxide - metabolism; Nitric Oxide Synthase - metabolism; Oligonucleotides, Antisense - pharmacology; Oxadiazoles - pharmacology; Phenylephrine - pharmacology; Quinoxalines - pharmacology; Rats; Rats, Wistar; Signal Transduction - drug effects; Up-Regulation; Vasoconstrictor Agents - pharmacology; Vasodilation; Vasodilator Agents - pharmacology; Immunohistochemistry; Agonist; Endothelial cell; Senescence; Calcium; Rat; α1-Adrenergic receptor; Cardiovascular disease; Inorganic element; Vascular disease; Arginine; Atherosclerosis; Phenylephrine; Immunoblotting assay; Aorta; Vasoconstrictor agent; Antihypotensive agent; Rodentia; Bioavailability; Antisense oligonucleotide; Endothelium; Polymerase chain reaction; Vertebrata; Mammalia; Treatment; Aminoacid; Animal; Ring; Nitric oxide; Neurotransmitter; Surgical approach; α-Adrenergic receptor agonist; Acetylcholine; aging; Comparative study
• ISSN: 0194-911X; 1524-4563
• DOI: 10.1161/01.HYP.0000198543.34502.d7

Arginase, expressed in endothelial cells and upregulated in aging blood vessels, competes with NO synthase (NOS) for l-arginine, thus modulating vasoreactivity and attenuating NO signaling. Moreover, arginase inhibition restores endothelial NOS signaling and l-arginine responsiveness in old rat aorta. The arginase isoform responsible for modulating NOS, however, remains unknown. Because isoform-specific arginase inhibitors are unavailable, we used an antisense (AS) oligonucleotide approach to knockdown arginase I (Arg I). Western blot and quantitative PCR confirmed that Arg I is the predominant isoform expressed in endothelialized aortic rings and is upregulated in old rats compared with young. Aortic rings from 22-month-old rats were incubated for 24 hours with sense (S), AS oligonucleotides, or medium alone (C). Immunohistochemistry, immunoblotting, and enzyme assay confirmed a significant knockdown of Arg I protein and arginase activity in AS but not S or C rings. Conversely, calcium-dependent NOS activity and vascular metabolites of NO was increased in AS versus S or C rings. Acetylcholine (endothelial-dependent) vasorelaxant responses were enhanced in AS versus S or C treated rings. In addition, 1H-oxadiazolo quinoxalin-1-one (10 μmol/L), a soluble guanylyl cyclase inhibitor, increased the phenylephrine response in AS compared with S and C rings suggesting increased NO bioavailability. Finally, l-arginine (0.1 mmol/L)-induced relaxation was increased in AS versus C rings. These data support our hypothesis that Arg I plays a critical role in the pathobiology of age-related endothelial dysfunction. AS oligonucleotides may, therefore, represent a novel therapeutic strategy against age-related vascular endothelial dysfunction.